Identify the reason for the solubility of polar solute in polar solvent from the following.

What is the osmotic pressure of solution prepared by dissolving 3 gram solute in $2 \mathrm{dm}^3$ water at 300 K . (Molar mass of solute $=60 \mathrm{~g} \mathrm{~mol}^{-1}$, $\mathrm{R}=0.0821 \mathrm{dm}^3 \mathrm{~atm} \mathrm{~K} \mathrm{~mol}^{-1})$

Calculate the molar mass of solute when 4 g of it dissolved in $1 \mathrm{dm}^3$ solvent has osmotic pressure 2 atm at 300 K . [R $\left[=0.082 \mathrm{~dm}^3 \mathrm{~atm} \mathrm{~K} \mathrm{~mol}^{-1}\right]$

Calculate $\Delta \mathrm{T}_{\mathrm{f}}$ of aqueous 0.01 m formic acid if van't Hoff factor is 1.1

$$\left[\mathrm{K}_{\mathrm{f}}=1.86 \mathrm{~K} \mathrm{~Kg} \mathrm{~mol}^{-1}\right]$$